1. Field of the Invention
The present invention relates to an image forming apparatus used for, for example, a display panel. In particular, the present invention relates to an image forming apparatus, which includes a spacer between a first substrate having a plurality of electron-emitting devices and a second substrate opposingly disposed to the first substrate.
2. Related Background Art
In general, in an image forming apparatus having a first substrate on an electron source side and a second substrate on a display surface side, which are opposingly disposed to each other with a distance, a spacer made of an insulating material is sandwiched between the first substrate and the second substrate to obtain a necessary atmospheric pressure resistance. However, the spacer is charged to affect an electron trajectory near the spacer. Therefore, there is a problem in that a displacement of a light-emitting position is caused. This causes image deterioration such as a reduction in light-emitting intensity or color blurring at a pixel near the spacer.
As known in the art so far, in order to prevent the above-mentioned spacer from being charged, a spacer covered with a high resistance film is used.
More specifically, there has been known an image forming apparatus in which a plate shaped spacer covered with the high resistance film is disposed along a wiring on the first substrate and the high resistance film is directly connected with the wiring and an electrode on the second substrate by an electroconductive adhesive. In addition, there has been known an image forming apparatus in which spacer electrodes are provided above and below a spacer covered with the high resistance film and the spacer is sandwiched such that the high resistance film is in contact with the wiring and the electrode through the spacer electrodes (see U.S. Pat. No. 5,760,538, JP08-180821 A).
Also, it has been proposed that an electroconductive intermediate layer (spacer electrode) is provided on each of the first substrate side and the second substrate side of the spacer covered with the high resistance film to function as an electrode for controlling an electron beam trajectory (see U.S. Pat. No. 6,184,619, JP10-334834 A).
In the image forming apparatus in which the spacer electrodes are provided above and below the spacer covered with the high resistance film and the high resistance film is connected with the wiring on the first substrate and the electrode on the second substrate through the spacer electrodes, as described in JP 08-180821 A, an electric field is distributed near spacer electrode portions. The electric field is distributed substantially uniform in the longitudinal direction of the spacer but generated with high intensity as compared with the case where the spacer is not disposed. Therefore, in the case where the spacer is disposed, when misalignment is caused, impinging positions of electron beams emitted from adjacent electron-emitting devices are likely to extensively change. In addition, it has been found that the spacer electrodes cause discharging and thus a quality of an image is likely to significantly deteriorate. To cope with the deterioration, it is necessary to provide the spacer electrodes so as not to expose to the side surface of the spacer or to dispose the spacer with high precision. In any manner, an increase in cost is caused.
In the image forming apparatus described in JP 10-334834 A, the intermediate layer (spacer electrode) is exposed to the side surface of the spacer. Therefore, as in the case where the spacer electrodes in JP 08-180821 A are exposed to the side surface of the spacer, unless high alignment precision of the spacer is maintained, desired control cannot be performed. Thus, there is a problem in that an increase in cost is unavoidable. In addition, for example, when a pixel pitch is reduced, an emitting position of an electron beam approaches the spacer. As a result, it is necessary to design a new spacer electrode having a corresponding shape, which causes an increased cost.